JPS6320014B2 - - Google Patents

Description

[Detailed description of the invention] The present invention is used in the manufacturing process of semiconductor devices such as transistors and ICs, which is necessary for exposing and transferring a relatively small-area mask pattern onto a large-diameter wafer by a step-and-repeat method. This invention relates to an alignment stage that moves a wafer at high speed and performs high-precision mutual alignment of the mask and wafer.

In the current semiconductor device manufacturing process, a method is used in which a large number of identical patterns are exposed and transferred all at once using a mask with a larger area than the wafer.
As the pattern to be transferred becomes finer and the diameter of the wafer becomes larger, local misalignment of the transferred pattern caused by deformation of the wafer during the manufacturing process is becoming a problem, and step-and-repeat technology is being developed to deal with this problem. Research began on exposure transfer using this method. This method requires an X/Y stage that moves the wafer step by step at high speed and high precision, and a fine alignment mechanism that aligns the mask pattern according to local deformation of the wafer. The X/Y stage is a mechanism that is often used in addition to exposure equipment, but most of them are mounted on a 1-axis stage using contact guides that reduce friction, such as steel balls or rollers, with another 1-axis stage perpendicular to it. A mechanical drive mechanism such as a ball screw is used to drive each axis. For this reason, when moving at high speeds, vertical fluctuations and swings of the stage are added to the movement, making it impossible to achieve high precision.In addition, there are limits to high speeds due to mechanical drive, vibration during drive, and lubrication. It has been difficult to avoid contamination of wafers and masks with oil and a decrease in stopping accuracy due to the stick slip phenomenon. In addition, even with non-contact guides such as hydrostatic bearings using air, which are known to eliminate the drawbacks of contact guides, in a system in which single-axis stages are stacked, the influence of center of gravity fluctuation due to the movement of the upper stage causes a decrease in accuracy, so The only option for the side stage was to use a contact type guide. Furthermore, these stages do not take into account the alignment of the wafer to be placed on top of the wafer and the mask to be held separately in opposition to it, and a satisfactory alignment stage for step-and-repeat exposure has not yet been announced. I wasn't there.

In order to solve these problems, the present invention independently guides the movable table on which the wafer is placed using static pressure gas bearings in the X, Y, and Z directions, and also makes the drive source and its guide non-contact. It is a thing,
Furthermore, fine movement mechanisms in each axis direction used for the purpose of alignment are arranged to provide an alignment stage suitable for step-and-repeat exposure, which will be described in detail with reference to the drawings below.

FIG. 1 is a partially cutaway front view showing an outline of an embodiment of the alignment stage of the present invention, in which 1 is a surface plate whose upper surface is precisely finished to a flat surface, 2 is a movable table on which a wafer 3 is placed; It is held in a non-contact manner on the surface plate 1 by a static pressure gas bearing using air whose pressure is controlled and which is blown out from a small hole (not shown) arranged on the lower surface.

Reference numeral 4 denotes a movable body that moves the movable table 2 in one direction (left-right direction in the figure), and has a guide portion (shown in cross section in the figure) consisting of two mutually parallel opposing planes.
The gap between the movable base 2 and the movable base 2 is maintained in the same way as the gap between the surface plate 1 and the movable base 2 by gas blown out from small holes (not shown) in the movable base 2. Reference numeral 5 denotes another one-directional moving body, which moves the moving table 2 in a direction perpendicular to the paper surface in the figure. Further, the gap between the guide portion (not shown) of the movable body 5 and the movable table 2 also constitutes a static pressure gas bearing. Reference numeral 6 denotes a guide for guiding the movable body 5, and the gap between the guide and the movable body 5 constitutes a cylindrical static pressure gas bearing.
Reference numeral 7 denotes a moving yoke of a linear motor for driving the moving table 5, which is composed of a coil plate. Reference numeral 8 denotes a fixed yoke of the linear motor, which is composed of a magnetic circuit. The respective guide parts are crossed in a parallel cross shape, and the movable table 2 is held in the center of the parallel cross shape in close proximity to the guide parts, and the guide 6 of the coil plate (movable yoke) 7 is shared with the cylindrical hydrostatic gas bearing. The movable bodies 4 and 5 are moved in two orthogonal directions on the surface plate 1 by a feeding mechanism that is driven in a non-contact manner by a linear motor.

With such a configuration, the vertical direction of the movable table 2 is defined only by the surface plate 1, and is not affected even if the movable body 4 or 5 is displaced in the vertical direction. 9 is a mask, 10 is a mask holder,
The mask holder 10 is attached to the surface plate 1 by a support mechanism (not shown).
It is supported so that the relative position with respect to it does not change, and
The X/Y fine movement mechanism, which will be described later, is provided inside the
The position and direction of the mask 9 can be finely adjusted using the Z fine movement mechanism and the θ fine movement mechanism. It is necessary that the lower surface of the mask 9 and the upper surface of the wafer 3 be maintained at a preset distance of several μm to more than ten μm, and this mechanism in which the vertical movement of the moving table 2 is small is effective. FIG. 2 is a more detailed partially cutaway perspective view of the wafer moving mechanism outlined in FIG. 1. The respective gaps between the movable table 2 and the movable bodies 4 and 5 are supported by static pressure gas bearings and there is no friction at all, so the movement of the movable table 2 is completely independent in each orthogonal direction and there is no mutual interference. The linear motor in the embodiment shown in this figure has a rectangular coil wound around a flat plate as a moving yoke (coil plate) 7, and two coils as a fixed yoke 8.
Magnets 8a and 8b on opposite flat plates are used. Both ends of the coil of the moving yoke 7 are within the magnetic fields of magnets 8a and 8b, respectively, and arbitrary driving can be performed by controlling the coil current. The current can be controlled by measuring the position of the L-shaped mirror 11 with a laser interferometer (not shown) and calculating the error between this measured value and the desired position. Sufficiently precise control is possible due to the high precision of recent high-speed arithmetic circuits (particularly circuits using microcomputers, etc.).

FIG. 3 shows an embodiment in which a linear pulse motor is used as the linear motor, but since the linear pulse motor is a well-known technique, a description thereof will be omitted. In this case, the positional accuracy decreases, but the effect is that control becomes easier. Since the wafer moving mechanism according to the present invention has no mechanical friction, the positional accuracy when a linear pulse motor is used is only due to the error of the linear pulse motor.

FIG. 4 is an exploded perspective view showing an outline of an embodiment of the X/Y fine movement mechanism, Z fine movement mechanism, and θ fine movement mechanism whose explanations are omitted in FIG. 1, FIG. 5 is a sectional view thereof, and
The figure is also a sectional view taken along the line AA in FIG. 5 for explaining the operations of the X/Y fine movement mechanism and the θ fine movement mechanism. In these figures, 12 is a permanent magnet 13
(see Figure 5); 14 is a coil bobbin around which a conducting wire is wound; 15 is a coil bobbin 14;
16 is a hollow cylinder made of a rigid body that is supported by the inner periphery of the annular diaphragm like a coil bobbin. 17 is a mask holding part that holds the mask 9 by vacuum suction, for example. 18 is a vertical diaphragm. A thin metal wire 19 that has little expansion and contraction and can be freely bent in the lateral direction supports the wire 18 and is attached to the coil bobbin 14.
a highly rigid support plate fixed to the lower part of the
Numerals 1 and 22 are, for example, cylindrical electrostrictive elements that can be expanded and contracted by a minute amount in the axial direction of the cylinder by applying a voltage. One end of each of the electrostrictive elements 20 , 21 , 22 is fixed to the lower part of the cylinder 16 , and the other ends of each of the electrostrictive elements 20 , 21 , 22 are in contact with the mask holding part 17 via rigid balls 23 , 24 , 25 . Corresponding spring 2
6, 27, and 28. With this structure, when a precisely controlled current is applied to the conductor of the coil bobbin 14 from a power supply device (not shown), the coil bobbin moves a small amount in the Z direction due to the electromotive force, causing the annular diaphragm 15 to move by a small amount. It stops at a position that balances the elastic force. It is clear that the Z fine movement function of the mask 9 is achieved by this. At this time, the annular diaphragm 15 does not move in the X and Y directions due to its rigidity. Next, when a voltage is applied to the electrostrictive element 20 from another power source (not shown), the mask 9 is given a slight movement in the X direction. Further, when equal voltages are applied to the electrostrictive elements 21 and 22, the mask 9 is slightly moved in the Y direction, and when voltages of equal magnitude and opposite polarity are applied to the electrostrictive elements 21 and 22, The mask 9 is given a θ fine movement. Although movement in the X direction occurs along with the θ fine movement, the overall operation is not hindered by performing the θ positioning prior to the X and Y positioning. For these fine movement mechanisms, a stroke of at most 2 to 3 μm is sufficient;
It is also possible to use a well-known mechanical fine movement mechanism such as screw feeding. Furthermore, it is clear that the purpose of positioning can be achieved even if these fine movement mechanisms are placed on the upper part of the above-mentioned moving table 2 and give fine movement to the wafer 3.

Next, FIG. 7 is an exploded perspective view showing the outline of another embodiment of the Z fine movement mechanism, and FIG. , 32, and is installed in a magnetic circuit 34 including a permanent magnet 33. Further, 35 is an annular diaphragm. Here winding 3
If the same current is applied to the coils 0, 31, and 32, a Z fine movement can be obtained in exactly the same manner as the operation of the coil bobbin 14 and magnetic circuit 12 explained in FIG. Further, by applying separate currents to each of the windings 30, 31, and 32, the coil bobbin 29 is given a slight inclination with respect to the Z axis, and the mask 9 can also be given a slight inclination. This operation is performed when the upper surface of the wafer 3 facing the mask 9 has a slight inclination due to local deformation or the like.
It is effective when installed parallel to the surface of the

The X/Y fine movement, θ fine movement, Z fine movement, and tilt angle fine movement in the Z direction explained above are detected by the positioning detection microscope using a non-contact gap detector to detect the spatial position of the partial surface of the mask and the wafer facing it. It is optimally adjusted by the error detection signal,
Since these detectors are already known, their explanation will be omitted.

As explained above, according to the present invention, it is possible to move a wafer at high speed and with high precision.
Moreover, it is now possible to spatially align the mask with the opposing parts of the wafer with high precision, and even if the wafer is partially deformed, each part of the wafer can be aligned with high precision. be. Therefore, exposure and transfer of fine patterns can be performed even on large-diameter wafers. Moreover, it is possible to realize an excellent step-and-repeat exposure apparatus with short wafer movement time and short alignment time.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway front view showing an outline of an embodiment of the alignment stage of the present invention, FIG. 2 is a detailed partially cutaway perspective view of the wafer moving mechanism shown in FIG. 1, and FIG.
The figure is a partially cutaway perspective view of a different type of linear motor in Figure 2, Figure 4 is an exploded perspective view showing the fine movement mechanism incorporated in the mask holder in Figure 1, and Figure 5 is the mechanism in Figure 4. 6 is a sectional view taken along the line AA in FIG. 5, FIG. 7 is an exploded perspective view showing another embodiment of the Z fine movement mechanism shown in FIG. 4, and FIG. 8 is a sectional view of the mechanism shown in FIG. 7. It is. 1... surface plate, 2... moving table, 3... wafer,
4, 5... Moving body, 6... Guide, 7... Moving yoke of linear motor, 8... Fixed yoke of linear motor, 9... Mask, 10... Mask holder,
11... L-shaped mirror, 12... Magnetic circuit, 13...
... Permanent magnet, 14 ... Coil bobbin, 15 ... Annular diaphragm, 16 ... Hollow cylinder, 17 ... Mask holding part, 18 ... Wire, 19 ... Support plate, 20,
21, 22... Electrostrictive element, 23, 24, 25...
Rigid sphere, 26, 27, 28... Spring, 29... Coil bobbin, 30, 31, 32... Winding wire, 33...
...Permanent magnet, 34... Magnetic circuit, 35... Annular diaphragm.

Claims (1)

[Claims] 1. A movable body having a guide portion consisting of two mutually parallel opposing planes and guided by a hydrostatic gas bearing consisting of a pair of parallel cylindrical guides, with the guide of the movable yoke above the A feed mechanism that is driven non-contact by a linear motor that is common to a cylindrical static pressure gas bearing, and another feed mechanism of the same structure that is orthogonal to the feed mechanism, are arranged so that each guide part intersects in a parallel cross shape, and the central part of the cross cross shaped Separately, a moving table on which a wafer is mounted, which is floating on a rectangular planar static pressure gas bearing, is mounted on a surface plate with good processing accuracy, and a rectangular plate provided on the side of the moving table is installed. a wafer moving mechanism that is held close to the guide section by a planar static pressure gas bearing and moves in two orthogonal directions on the surface plate as the feeding mechanism moves; and an upper part of the wafer moving mechanism. An X/Y fine movement mechanism that is placed opposite to and close to the wafer movement mechanism and moves a minute distance in the same direction as the two movement directions of the wafer movement mechanism, and a Z fine movement mechanism that is orthogonal to this, and An alignment stage for step-and-repeat exposure, comprising a mask holder having a θ fine movement mechanism that rotates by a minute angle. 2. Claim No. 2 in which all or part of the X/Y fine movement mechanism, Z fine movement mechanism, and θ fine movement mechanism are provided on the moving stage side of the wafer movement mechanism, and all or part of the fine movement mechanism on the mask holder side is removed. The step-and-repeat exposure alignment stage described in item 1. 3 As an X/Y fine movement mechanism, one electrostrictive element is arranged in one direction and two parallel electrostrictive elements are arranged in the other direction, and the two parallel electrostrictive elements are 3. The step repeat exposure alignment stage according to claim 1, wherein the θ fine movement mechanism is eliminated by applying different voltages to the θ fine movement mechanism. 4 As the Z fine movement mechanism, an annular diaphragm whose outer periphery is fixed on a plane perpendicular to the Z fine movement direction is arranged, and a bobbin with three separate plate-shaped drive coils is attached to the inner periphery of the annular diaphragm. , a separately fixed annular magnetic circuit and the motive force of the current flowing through the three drive coils to slightly move the bobbin in the Z direction, and also make it possible to slightly change the inclination angle. The alignment stage for step-and-repeat exposure according to item 1 or 2.